Cancer is the second leading cause of human death next to coronary disease in the United States. Worldwide, millions of people die from cancer every year. In the United States alone, as reported by the American Cancer Society, cancer causes the death of well over a half-million people annually, with over 1.2 million new cases diagnosed per year. While deaths from heart disease have been declining significantly, those resulting from cancer generally are on the rise. Cancer is soon predicted to become the leading cause of death.
Cancer is an abnormal state in which uncontrolled proliferation of one or more cell populations interferes with normal biological functioning. The proliferative changes are usually accompanied by other changes in cellular properties, including reversion to a less differentiated, more developmentally primitive state. The in vitro correlate of cancer is called cellular transformation. Transformed cells generally display several or all of the following properties: spherical morphology, expression of fetal antigens, growth-factor independence, lack of contact inhibition, anchorage-independence, and growth to high density.
A soluble form of CD27 (sCD27), a 32-kD protein identical to the extracellular domain of membrane-bound CD27, can be released after lymphocyte activation by differential splicing of the receptor protein or shedding from the cell surface by proteases. The production of sCD27 upon T-cell activation has been demonstrated previously by using anti-CD3 or a combination of anti-CD3 with anti-CD2 monoclonal antibody (MAb) to stimulate human peripheral blood mononuclear cells (PBMC) in vitro. sCD27 has been detected in serum, plasma, and urine samples from healthy individuals, and increased levels have been documented in systemic lupus erythematosus, viral infections, and lymphoid malignancies. The level of sCD27 in plasma samples has been used as a marker of disease burden in subjects with Waldenstroms macroglobulinemia and to monitor immune activation during antiretroviral therapy in subjects with HIV.